Image exposure apparatus

Abstract

Apparatus for performing imagewise exposure of a light-sensitive material whose spectral sensitivity is dependent on wavelength, uses a light source that emits light at a wavelength in the neighborhood of a narrow wavelength range and which is compensated for variations in its optical output level and wavelength on account of the change in the temperature of the light source. A drop in the exposure sensitivity of the light-sensitive material is prevented and a high-quality image is produced by electrically compensating for variations in the optical output level of the light source on the basis of the sensitivity vs. wavelength characteristics of the light-sensitive material and the wavelength vs. temperature characteristics of the light source so that the light source will produce a constant optical output in spite of the variations in wavelength due to the changes in its temperature. The apparatus also produces a high-quality color image having high color densities and good color balance by controlling the optical output levels of respective one of a plurality of sources of light at different wavelengths so that the exposure sensitivities of the light-sensitive material for different lights will not deteriorate in the face of temperature-dependent variations in the wavelengths of light emitted from the respective light sources.

What we claim is: 
     
       1. An image exposure apparatus which comprises: a light source for exposing a light-sensitive material with light having a predetermined wavelength; a drive source for driving said light source; a photodetector for detecting the optical output of said light source; a comparator for comparing the detected optical output level with a reference level; a temperature detector for detecting the change in the temperature of said light source; and control means which controls the optical output level of the light source on the basis of both the temperature change signal detected with said temperature detector and the output signal from said comparator in such a way that the exposure sensitivity of said light-sensitive material will not deteriorate in the face of the variation in the wavelength of light from said light source that occurs on account of the change in its temperature. 
     
     
       2. An image exposure apparatus according to claim 1 wherein said control means has a memory for storing the wavelength vs. temperature characteristics of the light source and the sensitivity vs. wavelength characteristics of the light-sensitive material, and an arithmetic processing unit which, in response to said temperature change signal, computes an optical output level for preventing the deterioration of the exposure sensitivity of said light-sensitive material on the basis of said wavelength and sensitivity characteristics, and which outputs an optical output control signal for controlling said drive source in such a way that said light source will produce the computed optical output level. 
     
     
       3. An image exposure apparatus according to claim 1 or 2 wherein the optical output control signal produced from said control means is supplied to the reference level input of said comparator and controls said reference level in such a way that the output signal from said comparator is supplied to said drive source so as to control the optical output level of said light source. 
     
     
       4. An image exposure apparatus according to claim 1 wherein said control means has a memory for storing the wavelength vs. temperature characteristics of the light source an the sensitivity vs. wavelength characteristics of the light-sensitive material, and an arithmetic processing unit which, in response to said temperature change signal and the output signal from said comparator, computes an optical output level for preventing the deterioration of the exposure sensitivity of said light-sensitive material on the basis of said wavelength and sensitivity characteristics, and which outputs an optical output control signal for controlling said drive source in such a way that said light source will produce the computed optical output level. 
     
     
       5. An image exposure apparatus according to claim 1 or 4 wherein the output signal from said comparator is supplied to the control means and the optical output control signal computed by said control means on the basis of said output signal is directly supplied to said drive source so as to perform direct control on the optical output level of said light source. 
     
     
       6. An image exposure apparatus which comprises; a plurality of light sources each for exposing a light-sensitive material with light having a predetermined wavelength to form a color image; and for each of said light sources a respective drive source for driving said light source, photodetector for detecting the optical output of said light source, comparator for comparing the detected optical output level with a reference level, and temperature detector for detecting the change in the temperature of said light source; said image exposure apparatus further including control means which controls the optical output levels of the light sources on the basis of both the temperature change signals detected with said temperature detectors and the output signals from said comparators in such a way that the exposure sensitivity of said light-sensitive material will not deteriorate in the face of variations in the wavelengths of light from said light sources that occurs on account of the change in temperature.   
     
     
       7. An image exposure apparatus according to claim 6 wherein said control means has a memory for storing the wavelength vs. temperature characteristics of the light sources and the sensitivity vs. wavelength characteristics of the light-sensitive material, and an arithmetic processing unit which, in response to said temperature change signals, computes an optical output level for each light source for preventing deterioration of the exposure sensitivity of said light-sensitive material on the basis of said wavelength and sensitivity characteristics, and which outputs optical output control signals for controlling said drive sources in such a way that said light sources will produce the computed optical output levels. 
     
     
       8. An image exposure apparatus according to claim 6 or 7 wherein an optical output control signal produced from said control means is supplied to the reference level output of at least one of said comparators and controls said reference level in such a way that the output signal from the comparator is supplied to its respective drive source so as to control the optical output level of its respective light source. 
     
     
       9. An image exposure apparatus according to claim 6 wherein said control means has a memory for storing the wavelength vs. temperature characteristics of each of said light sources and the sensitivity vs. wavelength characteristics of the light-sensitive material, and an arithmetic processing unit which, in response to a temperature change signal and the output signal from a comparator of an associated light source level for preventing the deterioration of the exposure sensitivity of said light-sensitive material on the basis of said wavelength and sensitivity characteristics, and which outputs an optical output control signal for controlling the drive source of said associated light source in such a way that said associated light source will produce the computed optical output level. 
     
     
       10. An image exposure apparatus according to claim 6 or 9 wherein the output signal from comparator associated with a light source is supplied to the control means an the optical output control signal computed by said control means on the basis of said output signal is directly supplied to the drive source of the light source associated with the comparator so as to perform direct control on the optical output level of said light source.